Electroluminescent display device with improved segmented electrode and terminal structure



June 13, 1967 E BUCK, JR, ETAL 3,325,664

ELECTROLUMINESCENT DISPLAY DEVICE WITH IMPROVED SEGMENTED ELECTRODE ANDTERMINAL STRUCTURE Filed Aug. 18, 1964 SUPPLY W mr FIG.2.

INVENTORS Ivon E. Buck,Jn B Rober? W. Wollenfin United States PatentVania Filed Aug. 13, 1964, Ser. No. 390,289 8 Claims. (Cl. 313-108) Thisinvention relates, generally, to electroluminescent devices and, moreparticularly, to electroluminescent display devices of a segmented ordigital type.

Electroluminescent devices normally comprise a metallic backing platewhich acts as one electrode, a layer of phosphor impregnated in adielectric coated thereover, and `a -light transmitting electrode overthe phosphor-dielectric layer. The light-transmitting electrode normallycomprises a layer of tin oxide on a glass foundation although otherlight-transmitting, electrically continuous materials may be substitutedtherefor, such as a layer of copper iodide deposited directly onto thephosphor-dielectric layer. If desired the phosphor material and thedielectric material may be applied as separate layers. In theconventional electroluminescent device, a metallic backing plate, whichmay be composed of steel or aluminum, mechanically supports the otherlayers of the device which yare quite thin and have little mechanicalstrength.

The usual construction of a segmented metal-ceramic lamp, such as adigit display device, requires intricate and diicult configuration onthe front transparent electrode. In addition, the problems of mountingand insulating contact members and sealing are considerably increased. Acertain amount of masking is also required to conceal the leads to theelectrode segments.

An object of this invention is to simplify and improve the structure ofa metal-ceramic segmented electroluminescent device.

A more specific object of the invention is to eliminate the foregoingundesirable characteristics of prior electroluminescent devices bysegmenting the rear electrodes instead of the front electrodes.

Another object of the invention is to provide means for supporting andinsulating the segmented rear electroties of such a device.

A further object of the invention is to provide contact members for thefront and the rear electrodes to which electrical connections may bereadily made at the rear of the electroluminescent device.

Other objects of the invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of the invention, the rear metalelectrode of an electrolumin'escent device is constructed of preformedindividual segments embedded in a ceramic insulating material capable ofsupporting the other laminations or layers of the device. A contact pinwhich is joined to or constitutes an integral part of the metalelectrode segments extends through the ceramic material to the rear ofthe device where it is accessible for making electrical connectionsthereto. An additional contact pin which is connected to the frontelectrode also protrudes through the ceramic material to the rear of thedevice. The electrode segments may be of a variety of shapes such aswords, letters of the alphabet, numerals, geometrical figures or digitaldisplay members which are preformed from enameling steel, aluminum orother sheet metal. They can also comprise preshaped metal forms orcastings. The embedding lCC ceramic is capable of being red with themetal without fracturing or softening.

For a better understanding of the nature and objects of the invention,reference may be had tothe following detailed description, taken inconjunction with the accompanying drawing, in which:

FIGURE 1 is a view, in front elevation, of an electroluminescent deviceembodying principal features of the invention;

FIG. 2 is a View, in section, taken along the line II--II in FIG. 1, and

FIGS. 3 to 6, inclusive, are views, in front elevation, of differentmodifications of the invention illustrated in FIGS. l and 2.

Referring to the drawing, and particularly to FIGS. 1 and 2, theelectroluminescent device 10 shown therein comprises alight-transmitting front electrode 11, a composite rear electrodeconsisting of a plurality of metal segments 12, and a layer 13 ofelectroluminescent phosphor disposed between the front and rearelectrodes. The front electrode 11 consists of a thin,light-transmitting, electrically-conducting layer of tin oxide, or othersuitable material, and has a transparent cover coating 15 thereover. Thecover coating 15 may be fused glass or a suitable transparent plasticmaterial. Ot-her materials such as, for example, indium oxide, bismuthoxide or aluminum oxide may be utilized in place Of the tin oxide.

The phosphor layer 13 may comprise any electroluminescent phosphormaterial which can be energized by an electric field to produce visiblelight. As a specific example, the electroluminescent material maycomprise zinc sulfide activated by copper and coactivated by chlorine,or others which are well known to the art.

The rear composite electrode comprises a plurality of preformed planarmetal segments 12 of preselected configuration eac-h one of which has aconducting member or pin 17 extending from its rear surface. The planarelectrode segments may be formed from a suitable metal such as, forexample, enameling steel or aluminum.

In order to insulate and support the metal electrode segments 12 andalso to support the `other layers of the device, the aforesaid electrodesegments are embedded in and thus hermetically united to front face ofan insulating glass or ceramic member 18. As shown in FIG. 2, theelectrode segments 12 are so embedded that their exposed surfaces areyflush with the front face of the support member 18 thereby providing asubstantially at supporting surface for the other layers of the device.The pins 17 protrude through the glass or ceramic member 18 to the rearof the device and thus provide an exposed terminal for electricalcontact to each, or simultaneously to a multiplicity, of the metalelectrode segments 12. The embedding ceramic or glass must be capable ofbeing tired with the -metal electrode segments without fractun'ng orsoftening. A ceramic or porcelain enameling frit having a high softeningpoint (900 C.1050 C. for example) and Ka suitable coefiicient ofexpansion may be utilized to form the supporting member 1S.

As shown most clearly in FIG. 2, -a ground coat layer 21 of suitableinsulating material, such as a titania precipitating glass of the typedisclosed in U.S. Patent No. 3,073,982, may be provided over the metalelectrodes 12 or over the entire surface of the sub-assembly. Also, adielectric breakdown layer 22 of 65% to 95% barium titanate embedded inglass may be provided between the ground coat layer 21 and the phosphorlayer 13. As a specific example, the aforesaid ground coat layer maycomprise a glass having the following composition (percent by wt.);l0.5%NagO, `35% KZO, 14.0% B203, 45% SiOz, 20.0% TiO2, `2.0% P205 and 5.0%F2. Any Ti02 3 frecipitating glass which can be enameled can be used ndfrom 0.001 to 30.0% of BaTiO3 may also be added.

The glass constituting the dielectric breakdown layer 2 must have `arelatively low firing temperature to avoid amaging the phosphor. Asuitable glass is as follows percent by wt.); 15.4% ZnO, 31.7% tBaO;19.1% B203, SiO2, 7.7% KZO, 3.81% NaZO, 1.3% lLiZO, l3.9% 1203, 11.2%TiOz and 1.9% Sb203.

As lis also shown in FIG. 2, one terminal of an alternatug currentsupply source is connected by a conductor .9 to a conducting member orpin 23 which extends hrough the ceramic member 18, the ground coat layerb1, the dielectric layer 22 and the phosphor layer 13 and s inelectrical contact with the front transparent electrode .1 at an area24. The pin 23 may be attached to the :lectrode 11 as by soldering. Theother terminal of the tlternating current supply is connected by anothercon luctor 19 to the arm 25 of a switch 26 that is adapted o selectivelyenergize the rear electrode through a series )f contacts and conductors20` that connect with the termi- 1al pins 17 attached to the respectivemetal electrode segnents 12.

Thus, in a manner well known in the art, any one of yhe electrodesegments 12 may be energized to illuminate t preselected portion of thedevice 10. When the arm 25 )f the switch 26 is in the posi-tion shown inFIG. 2, the lppermost electrode segment 12 is energized and the cor-'esponding portion of the device (the shaded area 27 of FIG. 1) isilluminated. The other areas 28 and 29 may be ,lluminated by rotatingthe switch arm 25 to energize the :orresponding rear electrode segments.

As a variation of the construction shown in FIG. 2, 11e metal electrodesegments 12 may be disposed on and De hermetically bonded to the frontsurface of the ceramic supporting member 18 with the pins 17 insertedthrough holes in the ceramic member. In this case the electrode segments12 would be insulated from each other by the ground coat layer 21instead of the ceramic member 1S.

It is apparent that an electroluminescent device of the type hereindescribed has numerous applications. Thus, as shown in =FIG. 3, Iadevice a may be fabricated wherein the rear electrode means comprise aplurality of segments preformed into le ters of the alphabet which arearranged to convey desired information. In the illustrated example, allof the electrode segments 31, 32 and 33 are energized simultaneously toilluminate the areas for the letters of the three words constituting thesign. Each letter of the rear electrode means has a conductor pinsecured to its rear surface, which pin is connected to one terminal ofthe alternating current supply. The other terminal of the supply isconnected to the light-transmitting electrically common front electrodemeans at the contact area 24a.

The embodiment 10b of the invention illustrated in FIG. 4 may beutilized in connection with a temperature indicator or other device toconvey and display certain information. In this case, one or more of theareas 34 corresponding to the rear electrode segments is illuminated inaccordance with the information received from the transmitting device.

As shown in FIG. 5, the rear metal electrode segments may also besymmetrically arranged to provide a device 10c wherein preselected onesof the segments may be energized to illuminate a numerical digit. Thus,areas 35, 36 and 37 may be illuminated to produce the numeral 7. Otherdigits from zero to nine may be produced by energizing the propersegments to illuminate the corresponding areas. The device 10e shown inFIG. 5 may also be utilized to produce numerous letters of the alphabet.

In the modification shown in FIG. 6, the rear metal electrode segmentsof the display device 10d are preformed into numerical digits which maybe arranged horizontally in a desired manner. These segments areselectively energized to convey information by illuminating thecorresponding areas. As illustrated, the areas 38 and 39 are illuminatedto produce the numeral 60. Other areas may -be illumina-ted to produceother numerals. It is obvious that other applications of theelectroluminescent device may be made.

From the foregoing description it will be apparent that the inventionprovides a simplified and economical construction for a metal-ceramicsegmented electroluminescent device. The ceramic member is utilized as asupport for both the metal electrode segments and the overlyinglaminations or layers that comprise the electroluminescent cell. In thismanner the device is provided with suiiicient rigidity to withstand theabuse sustained in commercial use. Moreover, since the metal electroderather than the light-transmitting front electrode is segmented to formthe desired indicia, electrical connection with the various segments canbe readily accomplished by pins or the like that extend directly throughthe back of the device. The sealing and masking problems associated withthe prior art practice of segmenting the front lighttransmittingelectrode are thus eliminated.

Since numerous changes may be made in the above desired construction anddifferent embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all subjectmatter contained in the foregoing description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

We claim as our invention:

1. Au electroluminescent display device comprising, front and rearelectrode means having a continuous layer of electroluminescent phosphordisposed therebetween, said front electrode means comprising acontinuous layer of light-transmitting material, said rear electrodemeans including a plurality of individual preformed planar metalsegments each having an elongated conducting member secured thereto, aninsulating member of `glass or ceramic material supporting the metalsegments and phosphor layer in operative relationship with the frontelectrode means, said planar metal segments being ernbedded in andhermetically united to the front face of said insulating support member,sai-d conducting members protruding through the insulating-supportmember to the rear of the device and thereby providing exposed terminalsfor the respective metal electrode segments, and an additional elongatedconducting member connected to the front electrode means and extendingthrough the phosphor layer and insulating-support member to the rear ofthe device,

2. An electroluminescent display device as set forth in claim 1 whereinsaid elongated conducting members comprise metal pins that are joined tothe rear surfaces of said first and second electrode means and are alsoembedded in the insulating-support member.

3. The electroluminescent display device set forth in claim 1 wherein;said insulating-support member is of substantially planar configuration,and the exposed surfaces of the embedded planar metal segments togetherwith the intervening portions of said insulating-support member dene asubstantially iiat supporting surface for the overlying layers of thedevice.

4. The electroluminescent display device set forth in claim 1 whereinsaid insulating-support member has a softening point of at least 900 C.and is thus adapted -to be fired with the metal electrode segmentswithout fracturing or softening.

5. The electroluminescent display device set forth in claim 1 wherein;the front face of said insulating-support member is of substantiallyplanar configuration, the planar metal electrode segments are disposedon the front face of said member, and a continuous layer of fused yglasscovers said metal electrode segments and hermetically secures them tothe front face of said member.

6. The electroluminescent display device set forth in claim 5 whereinsaid elongated conducting members comprise rigid metal pins that extendthrough holes in the insulating-support member.

7. In an electroluminescent display device having a plurality ofseparately energizable segments, the improvement which comprises thecombination of a like number of preformed sheet metal electrodesegments, a ceramic insulating member that is hermetically bonded to andholds the metal electrode segments in their assembled relationship, anda pin terminal joined to the rear surfaces of each of the metalelectrode segments and extending through said ceramic insulating memberto the rear of said device, said terminals and electrode segments beingsupported in the aforesaid relationship by said ceramic member.

8. An integral electrode-and-supporting assembly adapted for use in asegmented electroluminescent display device comprising, a rigidinsulator body of glass or ceramic having a softening point of about 900C a plurality of spaced thin metal electrode segments her- 6 meticallybonded to one side of said body, and a corresponding number of rigidconductor members joined to the bonded side of the respective electrodesegments and extending through and beyond said body, said electrodesegments and joined conductor members being held in predetermined arraysolely by said insulator body.

References Cited UNITED STATES PATENTS 2,922,993 l/1960 Sack 313-108 X2,988,661 6/1961 Goodman 313-108 3,246,193 4/1966 Dickson 313-1083,260,880 7/1966 Kupsky 313-108 X JAMES W. LAWRENCE, Primary Examiner.

R. JUDD, Assistant Examiner.

1. AN ELECTROLUMINESCENT DISPLAY DEVICE COMPRISING, FRONT AND REARELECTRODE MEANS HAVING A CONTINUOUS LAYER OF ELECTROLUMINESCENT PHOSPHORDISPOSED THEREBETWEEN, SAID FRONT ELECTRODE MEANS COMPRISING ACONTINUOUS LAYER OF LIGHT-TRANSMITTING MATERIAL, SAID REAR ELECTRODEMEANS INCLUDING A PLURALITY OF INDIVIDUAL PREFORMED PLANAR METALSEGMENTS EACH HAVING AN ELONGATED CONDUCTING MEMBER SECURED THERETO, ANINSULATING MEMBER OF GLASS OR CERAMIC MATERIAL SUPPORTING THE METALSEGMENTS AND PHOSPHOR LAYER IN OPERATIVE RELATIONSHIP WITH THE FRONTELECTRODE MEANS, SAID PLANAR METAL SEGMENTS BEING EMBEDDED IN ANDHERMETICALLY UNITED TO THE FRONT FACE OF SAID INSULATING SUPPORT MEMBER,SAID CONDUCTING MEMBERS PROTRUDING THROUGH THE INSULATING-SUPPORT MEMBERTO THE REAR OF THE DEVICE AND THEREBY PROVIDING EXPOSED TERMINALS FORTHE RESPECTIVE METAL ELECTRODE SEGMENTS, AND AN ADDITIONAL ELONGATEDCONDUCTING MEMBER CONNECTED TO THE FRONT ELECTRODE MEANS AND EXTENDINGTHROUGH THE PHOSPHOR LAYER AND INSULATING-SUPPORT MEMBER TO THE REAR OFTHE DEVICE.